The present invention relates to oral implants and, more particularly, to maxillary oral implants for use in patients who have enlarged sinus cavities.
The maxillary sinuses of a person are located on each side of the maxilla between the canine eminence and the tuberosity. The lowest point of the sinus floor usually lies superior to the first molar and the second premolar. However, the maxillary sinus shape varies greatly from one side of a person's face to the other, and from individual to individual.
As a person ages, the maxillary sinuses grow at the expense of the bone. Also, disease may cause resorption of bone. When bone loss occurs between the sinus floor and the dental arch, the feasibility of using maxillary dental implants is decreased.
Dental or oral implants are blades or screws with attached posts. These implants are surgically implanted in a patient's mandibule or maxilla along the occlusal plane. The implantation is achieved by exposing the bone with an incision through the gum tissue and creating a groove in the bone with a burr or drill. The implant blade is then wedged into the groove so that the post protrudes. Then the tissue is sutured about the bone and the base of the post. Finally, the post is used to mount an artificial dental appliance, such as a bridge.
A patient with an enlarged maxillary sinus has little bone in the maxilliary dental arch for accomodating the insertion of an implant. Consequently, the implantation procedure may result in the penetration of both the Schneiderian membrane on the sinus floor and the sinus itself. This may promote sinus infection and may result in the implant being only loosely held in the remaining bone, so that it fails to function effectively as a support for artificial teeth.
In U.S. Pat. No. 4,521,192 of the present inventor, there is suggested a technique for lifting the Schneiderian membrane and locating bone fragments beneath it in order to thicken the bone at the sinus floor by regrowth of new bone around the inserted the bone fragments. According to this suggestion, an implant is used which has a basket or cradle built into the blade portion. This basket is open toward the groove in the patient's bone and is filled with bone chips or fragments. Consequently, when the blade is wedged in the groove, the basket is moved to the base of the groove which, if the Schneiderian membrane is exposed, pushes the membrane upward into the maxillary sinus cavity.
The depth at which the blade of an implant is located in the patient's bone cannot be varied to any great extent with this prior apparatus. Thus, with this prior device, in which the basket is fixed to the blade portion of the implant, there is little control over the degree to which the Schneiderian membrane is lifted. This limits the oral surgeon's ability to increase the thickness of bone at the floor of the sinus cavity and to make it suitable for the retention of the implant.